Fuel tank

ABSTRACT

The invention relates to a fuel tank for a motor vehicle, comprising a tank body made from thermoplastic with a tank wall which defines a tank volume which can be closed in a substantially fluid-tight manner, with at least one filler opening and with one or more functional insert components which are arranged within the tank volume, at least one blind opening with a single use closure being provided in the tank wall.

FIELD

The invention relates to a fuel tank for a motor vehicle, comprising atank body made from thermoplastic with a tank wall which defines a tankvolume which can be closed in a substantially fluid-tight manner, withat least one filler opening and with one or more functional insertcomponents which are arranged within the tank volume and which areselected from a group comprising a fuel delivery unit which comprises atleast one baffle container and a fuel delivery pump, one or more suctionjet pumps, one or more filling level sensors, one or more venting valvesand one or more rollover safety valves.

BACKGROUND

Fuel tanks of this type are usually extrusion blow molded, deep drawn orinjection molded from thermoplastic. Such fuel tanks frequently consistof HDPE (high density polyethylene) or are produced on the basis of athermoplastic of this type. Polyethylene or other polyolefins are notdiffusion resistant with respect to hydrocarbons. For reasons ofemission protection, the known fuel tanks are as a rule produced frommultiple layer plastic extrudates which comprise barrier layers forhydrocarbons. Fundamentally, the aim is to produce the fuel tank withinsert components in such a way that as few openings as possible have tobe made in the tank wall. Openings in the tank wall are potentialleakage paths for hydrocarbons, since the integrity of one or morebarrier layers which are integrated into the tank wall can no longernecessarily be ensured in the region of an opening in the tank wall. Thetank wall frequently consists of five layer or six layer coextrudates ofthermoplastic with an EVOH layer (ethylene vinyl copolymer) which isembedded in adhesion promoter layers and is very thin in relation to theremaining layers of the tank wall. The plies or layers of the tank wallwhich are cut there are frequently not sealed or sealed merelyinsufficiently in the region of openings in the tank wall, with theresult that hydrocarbons can penetrate between the layers there and canlead to delamination of the layers. Moreover, the barrier layer of thetank wall is breached and interrupted in said region, with the resultthat leakage paths are produced in this way.

The magnitude of the leakage losses in the order of magnitude of a fewmilligrams per day is mainly also determined by the size of the openingswhich are to be provided in the tank wall.

One or more inspection openings which receive what is known as the fueldelivery unit are provided on typical fuel tanks for motor vehicles. Inthe case of a comparatively large fuel tank, two inspection openings ofthis type can be provided, for example. The inspection openings have adiameter which corresponds at least to the diameter of a fuel deliveryunit which is to be inserted into the fuel tank. A fuel delivery unit ofthis type as a rule comprises a baffle container, a fuel delivery pumpwhich is integrated into the baffle container, and at least one fillinglevel sensor for the baffle container.

Although modern production methods make it possible for the functionalinsert components which are to be accommodated in a fuel tank, such asair valves and venting valves, fuel delivery units, filling levelsensors, etc., to already be arranged in the tank volume during theproduction, it has to be possible in the case of a repair to service orreplace functional insert components of this type. Therefore, at leastone inspection opening is nevertheless to be provided in the tank wallof the fuel tank.

This (as a rule, largest) opening in the tank wall is also the greatestpotential leakage source, however.

A fuel tank is known from U.S. Pat. No. 6,179,145 B1. DE 10 2005 032 498A1 relates to a closure cap of a gasoline tank. DE 198 19 784 A1 relatesto a fuel tank having a closure which is to be opened merely inexceptional cases and is configured in one piece together with the fueltank in the production process.

A tear-off closure instead of a cap as paint animal protection is knownfrom DE 197 03 432 A1.

SUMMARY

The invention is based on the object of providing a fuel tank of thetype mentioned at the outset, which fuel tank is improved with regard topossible hydrocarbon emissions using simple means.

One aspect of the invention relates to a fuel tank for a motor vehicle,the fuel tank comprising a tank body made from thermoplastic with a tankwall which defines a tank volume which can be closed in a substantiallyfluid-tight manner, with at least one filler opening and with one ormore functional insert components which are arranged within the tankvolume and which are selected from a group comprising a fuel deliveryunit which comprises at least one baffle container and a fuel deliverypump, one or more suction jet pumps, one or more filling level sensors,one or more venting valves and one or more rollover safety valves, atleast one blind opening with a single use closure being provided in thetank wall.

The tank body of the fuel tank according to the invention can consist,for example, of a multiple layer extrudate comprising thermoplastic onthe basis of HDPE. The tank body can have been produced, for example, byway of extrusion blow molding or deep drawing. The tank body can havebeen joined together from two injection molded half shells or two deepdrawn half shells.

The tank wall preferably comprises structuring outer layers made fromHDPE with at least one EVOH barrier layer which is embedded in adhesionpromoter layers.

The functional insert components of the fuel tank can be provided ineach case in single or multiple form. They are expediently connected toone another functionally, for example by way of fuel lines, electriclines or venting lines which are laid within the tank volume.

A blind opening within the context of the present invention is anopening which is indicated in the tank wall by way of correspondingshaping and can be provided, for example, as a depression in the outertank wall. Within the context of the invention, a single use closure isto be understood to mean a closure of the blind opening, which closurecan be opened only exactly once and is then no longer available forrenewed closure of the tank volume.

The invention is based on the recognition that the functional insertcomponents which are provided within the fuel tank can be readilydesigned for the service life of the fuel tank and/or the motor vehicle,with the result that it is not as a rule required to open the fuel tankagain after completion, with the result that an inspection opening wouldin principle not be required. The maintenance possibility should beprovided, however, in particular for use conditions of the motorvehicle, in which high dust loading of the ambient air or contaminatedfuel are to be expected.

According to the invention, a fuel tank having a blind opening with asingle use closure is therefore provided, which blind opening does notform a breach or aperture of the tank wall. As a result, the fuel tankis completely impermeable in the region of the blind opening. In theregion of the blind opening, a barrier layer which is provided in thetank wall or an inner chemical treatment of the tank wall is completelyintact, with the result that the leakage potential of the fuel tank isreduced considerably by way of the above-described measures.

In addition, an inspection opening which can be opened and closed againusually requires that metallic closure elements are formed into the tankwall, which closure elements can absorb corresponding holdingforces/deformation forces during the closure of the inspection opening.To this end, metallic flange rings which are also called SAE rings areusually integrated into the tank wall. Said flange rings are providedwith holding claws or holding clamps which form a part of a bayonetclosure and engage over a closure cap. If the inspection opening in theconventional sense is dispensed with, it is likewise no longer necessaryto integrate a flange ring of this type into the tank wall, which leadsto a considerable weight saving for the fuel tank.

In one preferred variant of the fuel tank of the invention, it isprovided that the blind opening is covered and sealed outside the tankvolume by way of a closure cap, and that the closure cap is connectedreleasably to the tank wall.

Said closure cap is as a rule without function, since it has to ensurethe sealing action of the fuel tank only in the service or repair case.

The closure cap can be configured in such a way that it stabilizes thetank wall in the region of the blind opening.

The closure cap can be sealed, for example, by way of one or more O-ringseals in the blind opening which is preferably configured as an outerdepression in the tank wall. In this case, the closure cap which isintegrated into the blind opening stabilizes the blind opening againstlaterally acting forces.

The closure cap can be provided in such a way that correspondinglyconfigured holding claws or holding clamps or guide faces within theblind openings are not required. As has already been mentioned, theclosure cap is without function when the tank wall is intact in theregion of the blind opening, apart from the abovementioned stabilizingfunction.

The blind opening is expediently configured as an integral shaped-outformation of the tank wall.

In one advantageous variant of the fuel tank according to the invention,it is provided that the blind opening has a predetermined break line inthe tank wall, which predetermined break line defines a disk-shaped capwhich can be detached from the tank wall as a single use closure. In therepair or service case, the cap can be separated or detached from thetank wall, and a re-closure of the inspection opening which is producedin this way then takes place by means of the closure cap which thenfulfills the function which is intended for it.

According to the invention, the blind opening is expediently providedwith a surround with a thread. The thread is configured, for example, asan internal thread. The closure cap can be configured as a screw cap andcan likewise have a thread which is of complementary configuration withrespect to the thread of the surround.

The contour of the predetermined break line does not necessarily have tocorrespond to the contour of the surround. The surround can be, forexample, of circularly annular configuration, whereas the contour of thepredetermined break line is configured so as to differ therefrom.

In one particularly expedient refinement of the fuel tank according tothe invention, it is provided that the cap is provided with a grip tab,with the result that the cap can be detached from the tank wall in asimilar manner to the tab on a beverage closure. Here, the cap ispreferably delimited completely by a predetermined break line, with theresult that the cap can be removed completely from the tank wall. Thepredetermined break line preferably does not engage into the barrierlayer. The predetermined break line can be provided, for example, as aweakened line in an HDPE outer layer.

In one particularly expedient variant of the fuel tank according to theinvention, it is provided that the grip tab extends parallel to andpartially at a spacing from the cap, and is arranged eccentrically onthe cap, with the result that lever forces can be introduced via thegrip tab into the predetermined break line which delimits the cap.

As a protective means for the predetermined break line in the case of apossible side impact on the fuel tank, it is provided that the surroundis configured as a circumferential thickened bulge which has a greaterthickness than the tank wall outside the surround. As a rule, this willbe the tank wall of the top floor of the fuel tank, which tank wall canhave a thickness, for example, of from 3 to 10 mm. The tank wallexpediently has a thickness of approximately 5 mm, and thecircumferential bulge can be configured to be approximately twice asthick as the tank wall outside the surround.

As an additional or alternative measure for protecting the predeterminedbreak line against deformation forces which act for instance laterallyon the tank wall, one or more beads or corrugations or grooves which runaround the surround, act like a spring and absorb deformation forceswhich are introduced laterally into the tank wall can be provided in thetank wall.

Although it is not necessary in principle in the case of the fuel tankaccording to the invention to provide a metallic flange ring in theregion of the blind opening of the tank wall, this is not ruled outwithin the context of the invention.

The blind opening having the single use closure within the context ofthe present invention forms an inspection opening in the tank wall,which inspection opening can be produced once if required, that is tosay in the service case or in the repair case. The opening can then bere-closed by way of the closure cap which is provided as a reserveclosure.

Leadthroughs which are required, for instance, for an electricconnection of the fuel delivery unit and for delivering fuel to theinternal combustion engine of the motor vehicle can be provided at adifferent location in the tank wall. Said leadthroughs are comparativelysmall in comparison with an otherwise necessary inspection opening.

Overall, the leakage potential of the fuel tank according to theinvention has been reduced to approximately 50% of the leakage potentialof a comparable conventional fuel tank. Moreover, a weight saving of upto 1 kg is achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, the invention will be described using oneexemplary embodiment which is shown in the drawing, in which:

FIG. 1 shows a section through a part of the tank wall of a fuel tankaccording to the invention in accordance with a first exemplaryembodiment in the region of the closed blind opening;

FIG. 2 shows a section which corresponds to FIG. 1 through the tank wallof a fuel tank in the region of the blind opening in accordance with asecond exemplary embodiment of the invention;

FIG. 3 shows a section through a part of the tank wall of a fuel tankaccording to the invention in accordance with a third exemplaryembodiment in the region of the closed blind opening; and

FIG. 4 shows a section which corresponds to FIG. 3 through the tank wallof a fuel tank in accordance with a further exemplary embodiment of theinvention.

DETAILED DESCRIPTION

The fuel tank 1 according to the invention is not shown completely inthe figures. It comprises a tank body with a tank wall 2 made fromthermoplastic.

The tank wall 2 consists of a multiple layer extrudate made fromthermoplastics on the basis of polyethylene. Only two layers of the tankwall 2 are shown in outlines in the drawings, but the invention is to beunderstood in such a way that the tank wall 2 can certainly have aplurality of layers, for example said tank wall 2 can be configuredoverall with six layers and can comprise two structuring layers and atleast one barrier layer which is arranged in between.

FIG. 1 shows a section through the tank wall 2 in the region of a blindopening 3 which is configured as an integral shaped-out formation of thetank wall. The tank wall 2 encloses a tank volume 4 which is faced bythe inner side of the tank wall 2. On the side which faces away from thetank volume 4, the blind opening 3 is configured as a depression of thetank wall 2. The blind opening 3 therefore forms a blind bore in theouter side of the tank wall 2. On the outer side of the tank wall 2, theblind opening 3 is closed tightly by means of a screw cap 5. The blindopening 3 is delimited by way of a surround 6 which is provided with athread 7 which interacts with a corresponding thread 7′ of the screw cap5.

According to the invention, the blind opening 3 is configured as asingle use closure of the fuel tank 1, the single use closure beingformed by way of a disk-shaped cap 8 which is defined by way of acompletely circumferential predetermined break line 9 in the tank wall2.

The blind opening 3, the surround 6, the thread 7 of the surround andthe screw cap 5 are rotationally symmetrical and circular in the planview. A grip tab 10 is fastened to the cap 8 on that side of the cap 8which faces away from the tank volume 4. The grip tab 10 comprises afirst end 11 which forms the root region of the grip tab 10 and a secondend 12 which is configured as a grip end and projects from the outerface of the cap 8, with the result that it can be reached under there byway of a finger of the hand of an operator. The grip tab 10 is arrangedeccentrically on the cap 8 in such a way that the first end 11 of thegrip tab 10 adjoins the predetermined break line 9, with the resultthat, if the second end 12 of the grip tab is reached under, as shown inoutlines in FIG. 2, lever forces are introduced into the predeterminedbreak line 9 in such a way that first of all the cap 8 can be pressed indownward in the direction of the tank volume 4, with the result that thepredetermined break line 9 tears. The cap 8 can then be separatedcompletely from the tank wall 2 by way of pulling on the grip tab 10.

As has already been mentioned at the outset, the fuel tank iscommissioned with the closed blind opening 3. In this state, the tankvolume 4 in the region of the blind opening 3 is closed. The cap 8 isconnected fixedly to the tank wall 2, and the depression which is formedby way of the blind opening 3 in the tank wall 2 is covered by way ofthe screw cap 5. The screw cap 5 is sealed against a circumferentialsealing face of the surround 6 via a circumferential elastomer seal 13.In this state, as shown in FIG. 1, for example, the screw cap 5 issubstantially without a function.

In a service case which is not to be assumed, the screw cap 5 would haveto be opened. The cap 8 would have to be released from the tank wall 2via the grip tab 10, with the result that an inspection opening which isaccessible from the outside is then formed in the tank wall 2.

After the maintenance has been carried out, the screw cap 5 would haveto be inserted again into the opening which is produced in this way, thescrew cap 5 then actually being given the function of the sealing of thetank volume 4.

FIG. 2 shows a second exemplary embodiment of the invention, in whichidentical components are provided with identical designations. FIG. 2 atthe same time shows the partially open state of the cap 8 withdestruction of the tank wall 2 in the region of the predetermined breakline 9. The screw cap 5 which is also provided in this exemplaryembodiment of the invention is not shown in FIG. 2 also for reasons ofsimplification.

The exemplary embodiment according to FIG. 2 differs from that in FIG. 1in that two circumferential beads 14 which are arranged at a spacingfrom one another are provided in the tank wall 2, which beads 14 enclosethe surround 6 completely. FIG. 2 shows only one side of the tank wallwith the beads 14. The beads are arranged in each case in a circularcompletely circumferential manner at a spacing from the surround 6 andact as springs which absorb deformation forces which are possiblyintroduced laterally into the tank wall 2, and therefore prevent thepredetermined break line 9 from being loaded.

The exemplary embodiment according to FIG. 3 corresponds approximatelyto that according to FIG. 1, with the difference that an annular spacewhich is provided in the region of the surround 6 in the tank wall 2 onthe side which faces the tank volume 4 is filled by a supporting ring15. The supporting ring 15 forms a mechanical stabilization of thesurround 6 in such a way that the blind opening 3 or the predeterminedbreak line 9 is kept free from any impact-induced lateral forces. Thesupporting ring 15 can be configured as a metallic supporting ring. Asan alternative, the supporting ring 15 can also be configured from acomparatively strong thermoplastic. In this context, a strongthermoplastic can be understood to mean, for example, a glass fiberreinforced polyolefin. Otherwise, identical components are provided withidentical designations in the exemplary embodiment according to FIG. 3as in the remaining exemplary embodiments.

The exemplary embodiment according to FIG. 4 differs from that in FIG. 1to the extent that the surround 6 is formed by way of a fold of the tankwall 2, that is to say the tank wall 2 is configured to be twice asthick in the region of the surround 6 as in the remaining region of thetank wall 2, and forms a bulge-like thickened portion there. Otherwise,the exemplary embodiment according to FIG. 4 corresponds to that inFIG. 1. Identical components are provided with identical designations.

LIST OF DESIGNATIONS

-   -   1 Fuel tank    -   2 Tank wall    -   3 Blind opening    -   4 Tank volume    -   5 Screw cap    -   6 Surround    -   7 Thread of the surround    -   7′ Thread of the screw cap    -   8 Cap    -   9 Predetermined break line    -   10 Grip tab    -   11 First end of the grip tab    -   12 Second end of the grip tab    -   13 Elastomer seal    -   14 Beads    -   15 Supporting ring

What is claimed is: 1-10. (canceled)
 11. A fuel tank for a motorvehicle, comprising a tank body made from thermoplastic with a tank wallwhich defines a tank volume which can be closed in a substantiallyfluid-tight manner, with at least one filler opening and with one ormore functional insert components which are arranged within the tankvolume and which are selected from a group comprising a fuel deliveryunit which comprises at least one baffle container and a fuel deliverypump, one or more suction jet pumps, one or more filling level sensors,one or more venting valves and one or more rollover safety valves, atleast one blind opening with a single use closure being provided in thetank wall, the blind opening being covered and sealed outside the tankvolume by way of a closure cap, and the closure cap being connectedreleasably to the tank wall, characterized in that the blind opening hasa surround with an internal thread, and in that the surround isconfigured as a circumferential bulge which has a greater thickness thanthe tank wall outside the surround.
 12. The fuel tank as claimed inclaim 11, wherein the blind opening is configured as an integralshaped-out formation of the tank wall.
 13. The fuel tank as claimed inclaim 11, wherein the blind opening has a predetermined break line inthe tank wall, which predetermined break line defines a disk-shaped capwhich can be detached from the tank wall as a single use closure. 14.The fuel tank as claimed in claim 13, wherein the closure cap isconfigured as a screw cap and has a thread which is of complementaryconfiguration with respect to the thread of the surround.
 15. The fueltank as claimed in claim 13, wherein the cap is provided with a griptab.
 16. The fuel tank as claimed in claim 15, wherein the grip tabextends parallel to and partially at a spacing from the cap and isarranged eccentrically on the cap, with the result that lever forces canbe introduced via the grip tab into the predetermined break line whichdelimits the cap.
 17. The fuel tank as claimed in claim 11, wherein thetank wall has at least one bead which runs around the surround.